Typically, gas turbine engines include a compressor for compressing air, a combustor for mixing the compressed air with fuel and igniting the mixture, and a turbine blade assembly for producing power. Combustors often operate at high temperatures that may exceed 2,500 degrees Fahrenheit. Typical turbine combustor configurations expose turbine blade assemblies to these high temperatures. As a result, turbine blades must be made of materials capable of withstanding such high temperatures. In addition, turbine blades often contain cooling systems for prolonging the life of the blades and reducing the likelihood of failure as a result of excessive temperatures.
Typically, turbine blades are formed from a root portion having a platform at one end and an elongated portion forming a blade that extends outwardly from the platform coupled to the root portion. The blade is ordinarily composed of a tip opposite the root section, a leading edge, and a trailing edge. The inner aspects of most turbine blades typically contain an intricate maze of cooling channels forming a cooling system. The cooling channels in a blade receive air from the compressor of the turbine engine and pass the air through the blade. The cooling channels often include multiple flow paths that are designed to maintain all aspects of the turbine blade at a relatively uniform temperature. However, centrifugal forces and air flow at boundary layers often prevent some areas of the turbine blade from being adequately cooled, which results in the formation of localized hot spots. Localized hot spots, depending on their location, can reduce the useful life of a turbine blade and can damage a turbine blade to an extent necessitating replacement of the blade. Thus, a need exists for a cooling system capable of providing sufficient cooling to turbine airfoils.
One particular conventional cooling system is shown in FIGS. 1-3. This system includes a mid-chord serpentine cooling channel and a trailing edge cooling circuit that are separated from each other by a continuous rib. The mid-chord serpentine cooling channel may bleed off cooling fluids through a tip section exhaust channel that extends to the trailing edge at the tip section because the mid-chord region normally experiences a lower heat load than the rest of the airfoil. The tip section exhaust channel does not receive any cooling fluids from the trailing edge cooling circuit. By bleeding off cooling air from the mid-chord region, the tip section exhaust channel at the tip flag yields a low mass flux and a low cooling flow at a large flow area that causes a low internal heat transfer coefficient, which is insufficient to provide proper cooling for that region. Subsequently, overheating occurs at the blade tip flag location proximate to the trailing edge that is potentially damaging to the turbine blade. Thus, a need exists for a turbine blade with an improved cooling system that overcomes these shortcomings.